Downy Mildew - Diseases

Commonly asked question(s):

Is there any cure for downy mildew on busy lizzies?

You are not alone in your battle against downy mildew. This fungus is quite widespread and often affects Busy Lizzies during warm wet periods in summer, making the foliage turn yellow and drop, and eventually leaving just a mass of slimy stems with a tuft of yellow leaves at the tips. A diagnosis can normally be confirmed by checking for a white downy coating on the underside of the leaves that are still on the plant.

Copper based fungicides and those containing the active ingredient Mancozeb may help to prevent outbreaks. Once infected, the plants will gradually deteriorate and eventually die. If this occurs you will need to destroy all infected plant material to prevent spores reinfecting any remaining plants. We would advise against composting them as spores may remain in the compost heap and infect new plants next year. Burning them is the best option.

You might also like to try growing Sunpatiens®. This New Guinea hybrid appears to be less susceptible then the usual bedding Busy Lizzies (Impatiens walleriana).

Why are my busy lizzies dying in my flower ball?

Our guess is that they may have downy mildew. This is a fungus is quite widespread and often affects busy lizzies during warm wet periods of weather in summer, making the foliage turn yellow and drop, and eventually leaving just a mass of slimy stems with a tuft of yellow leaves at the tips. This can normally be confirmed by checking for a white downy coating on the underside of the leaves that are still on the plant.

Unfortunately there is little that can be done and the plants will deteriorate and eventually die. We would suggest burning them to prevent future outbreaks. We would advise against composting them as spores may remain in the compost heap and infect new plants next year. If you intend to reuse the flowerball next year, then it should be cleaned and disinfected.